On reversing propeller systems, it is desirable to accurately measure the propeller blade (or beta) angle. In this manner, it becomes possible to ensure that the blade angle is controlled according to the engine power set-point requested in reverse operation. Accurate measurement of the blade angle also ensures that the propeller is not inadvertently commanded to transition into low or reverse beta angles, which would cause a potentially serious condition for the aircraft.
Current turboprop propeller feedback systems typically use a mechanical cam and cables to provide a variable hydraulic lockout mechanism to prevent the propeller from transitioning into a low or reverse beta position. However, a drawback of such systems is that they do not interface well with digital control systems.
There is therefore a need for an improved propeller feedback system.